I'd like to reclaim pages for the memory region mapped by mmap(MAP_SHARED | MAP_ANONYMOUS).

For this purpose, I called madvise(MADV_DONTNEED) for this shared memory from all the processes that can see this shared region.

However, the physical pages for this shared region cannot be freed and the shared data remains on the shared memory.

How can you completely reclaim pages for the memory region mapped by mmap(MAP_SHARED | MAP_ANONYMOUS)?